For web apps, chrome has a throttling tool in the dev tools. Not sure how sophisticated it is, but I've used occasionally to recreate bugs only noticed by clients on slower connections.
As a designer + developer, it always frustrates me to see a design not translated into code well. If this is built using css, there really aren't any excuses for not making this look as slick as the visuals. Especially when the design doesn't appear to contain anything which looks especially difficult to recreate.
It's difficult to overemphasise how much this kind of thing gives users of your software confidence. The common assumption is, if it looks good, it works well (and the opposite).
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